A magnetic head and disk tester is an instrument that is used for testing the characteristics of magnetic heads and disks, such as a signal-to-noise ratio, track profile, etc. The tester should simulate those motions of the head with respect to the disk and the same rotational speeds of the disks that occur in an actual hard disk drive during operation. Each tester consists of two components, i.e., a mechanical component, commonly referred to as a spinstand, that performs movements of the head with respect to the disk, and an electronic component that is responsible for measurement, calculation, and analysis of the measured signal. The spinstand is also a mechanical component of a servo-writer, an instrument that is used for writing servo information on a magnetic disk, as well as a component of a flying height tester; an instrument used for measuring the flying height of a head over the disk.
Examples of prior art spinstands for a head and disk tester include the Guzik V2002 XY-positioning spinstand and the Guzik S-1701B Micro Positioning Spinstand, both of which are available from the assignee of the present disclosure, Guzik Technical Enterprises, 2443 Wyandotte Street, Mountain View, Calif. 94043, USA.
As the density of magnetic recording increases, additional information tracks are compressed into a given disk area. The decrease in track size heightens the demand for improved accuracy in head positioning. Likewise, the rotational speeds of the magnetic disks increase in order to achieve shorter access times. In addition, more disks are added to the disk stack to provide additional storage.
As the disk(s) rotate, vibrations in both the disks and the magnetic heads may be induced. These vibrations increase track misregistration. In some cases, track misregistration reaches unacceptable levels at which spinstand operation becomes unreliable.
A common prior art solution to this problem is a disk chuck consisting of a cap assembly and a base assembly. The cap and base assemblies clamp the disc to the spindle by use of a screw that passes through the cap and threads into the base. The screw attaches the cap to the base, clamping the disc with a force proportional to the fastening torque of the screw. This creates two problems. The force is dependant upon the fastening torque, which can vary from one assembly to another, and the screw must be manually inserted and removed with each disc change, adding time to the testing process.
Another prior art solution is a clamping mechanism for securing magnetic discs, shown in FIG. 8, comprised of a cap (6) and a base (9). The disc (7) is held between the cap (6) and the base (9). Vacuum, applied through a port in the base mounting screw (44), provides the clamping force. The vacuum is held constant using a U-Cup seal (43). The cap (6) is centered about the base (9) using a hardened pin (41) and locating bushing (45). When the cap (6) is inserted into the base (9), the pin (41) prevents the piston (42) from contacting the inside walls of the centering bushing (46). To remove the cap, positive air pressure is applied to the air passage (44), collapsing the walls of the U-Cup seal (43), forcing the cap (6) out of the base (9) without causing wear on the seal (43) or the sealing surface of the centering bushing (46). This method, used alone, requires physical interaction from the operator in the form of placing the cap on the base to secure the disk, and removing the cap after testing is complete to remove the disk.
What is still desired is a new and improved apparatus and method for quickly securing disks on a spindle of a spinstand. Among other aspects and advantages, the new and improved apparatus and method will automate a prior art clamping method by mechanically placing the cap of a vacuum chuck on a disk and mechanically remove the cap from the disk without any physical participation from the operator.